SERBIAN JOURNAL OF ELECTRICAL ENGINEERING
Vol. 17, No. 3, October 2020
CONTENTS
Novel Reversible CLA, Optimized RCA and Parallel Adder/Subtractor Circuits
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DOI: https://doi.org/10.2298/SJEE2003259G
Abstract: This paper proposes reversible circuit designs of the three most commonly used adders:
carry look-ahead adder (CLA adder), ripple carry adder (RCA adder), and parallel adder/subtractor.
The n-bit reversible CLA adder, called CLA-GH, is designed using the Peres and Fredkin gates.
The n-bit optimized reversible RCA adder, called ORCA-GH, is designed using the reversible circuit of
a parity-preserving reversible full adder. Both circuits reduce the quantum cost. However,
the ORCA-GH circuit also improves the number of constant inputs. Furthermore, the n-bit reversible parallel adder/subtractor,
called PAS-GH, is designed using the Feynman, Peres, and Fredkin gates. It decreases the number of garbage outputs and quantum cost.
The transistor realizations of the CLA-GH and PAS-GH circuits are provided accordingly.
The evaluation results indicate that the proposed circuits surpass the existing works in all figures of merit.
Keywords: Reversible Circuit Design, Carry Look-ahead Adder, Ripple Carry Adder, Parallel Adder/Subtractor.
Automatic Corrections of Human Body Depth Maps using Deep Neural Networks
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DOI: https://doi.org/10.2298/SJEE2003285G
Abstract: This paper presents an approach to correcting misclassified pixels in
depth maps representing parts of the human body. A misclassified pixel is a pixel of a depth map which,
incorrectly, has the 'background' value and does not accurately reflect the distance from the sensor to the body being scanned.
A completely automatic, deep learning based solution for depth map correction is proposed. As an input,
the solution requires a color image and a corresponding erroneous depth map. The input color image is segmented
using deep neural network for human body segmentation. The extracted segments are further used as guidance to
find and amend the misclassified pixels on the depth map using a simple average based filter.
Unlike other depth map refinement solutions, this paper designs a method for the improvement of the
input depth map in terms of completeness instead of precision. The proposed method does not exclude
the application of other refinement methods. Instead, it can be used as the first step in a depth map
enhancement pipeline to determine approximate depths for erroneous pixels, while other refinement
methods can be applied in a second step to improve the accuracy of the recovered depths.
Keywords: Depth Map Refinement, Human Body, Photogrammetry, Deep Learn¬ing, Segmentation.
Control of an Isolated Microgrid Including Renewable Energy Resources
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DOI: https://doi.org/10.2298/SJEE2003297F
Abstract: It is now more then a choice to use small-distributed generators (DGs)
based on renewable energy resources (RES) due to their benefits in minimizing environmental problems and simplifying power
system planning and operation. The integration of DGs in the main grid or in forming a standalone microgrid (MG)
is increasing day by day and became as an alternative solution to large conventional central power stations and as
a key for the electrification of rural areas. This paper presents an overall comparison of controlling the
MG system combining between different DGs in islanded mode. Energy management system (EMS) applied is mainly
an essential task to maintain an ideal flow of energy in-between generation and consumption, many are strategies to do so,
the artificial intelligence (AI) (highlighted) is one of the most advantages methods to help sizing, optimizing, and power energy managing.
To solve this problem in this paper we present a Fuzzy Logic Control of isolated MG in comparison with a classic
PI control system to see the different influences in maintaining stability in voltage and frequency output especially
in the standalone application. The considered HRES combines a wind turbine (WT) and photovoltaic (PV) and an energy storage system (ESS).
Simulation results obtained from MATLAB/Simulink environment demonstrates the effectiveness of the proposed intelligent artificial algorithm.
Keywords: Micro-Grid, Fuzzy logic controller, Renewable Energy Sources, Wind-PV-Battery System,
PI classical controller, Voltage Source Inverter, Energy Management System.
An Enhanced Exponential Reaching Law Based Sliding Mode Control Strategy for a Three Phase UPS System
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DOI: https://doi.org/10.2298/SJEE2003313N
Abstract: UPS is used to deliver a high quality sinusoidal waveform to
consumers without any interruptions. This work proposes an Enhanced Exponential Reaching Law (EERL) based
Sliding Mode Control (SMC) for a three- phase UPS 30 kVA system used in industrial Applications.
The work presents the application of proposed controller on the rectifier side as well as on the
inverter side feeding a linear and/or a nonlinear load. Mathematical models of the three phase rectifier (AC/DC)
and three phase inverter (DC/AC) are derived. Frequency response characteristics are plotted to observe
the system stability using state feedback approach. A DC/DC buck/boost converter is utilised for
charging and discharging of battery which acts as a secondary power source for the UPS to feed critical loads.
It also maintains power balance. The design of SMC, HOSMC and EERL-SMC are presented. The EERL based SMC
is used in this work to obtain a pure sinusoidal waveform with less settling time compared to a conventional SMC.
It is robust against sudden changes in load and is more efficient compared to SMC and higher order
sliding mode controller (HOSMC). Using EERL, chattering phenomenon can be very much reduced with less steady state error.
Chattering is observed through phase plane plots in this paper. The system is presented with both linear and nonlinear loads.
A comparison is brought with respect to a classical SMC and a higher order SMC (super twisting algorithm) for a UPS system.
EERL-SMC performs better in terms of pure sinusoidal waveform, good tracking, less settling time (4ms) and
less steady state error (1.74%) with low THD (0.12%). It can be an alternative to a HOSMC. Simulation studies
are presented in PSCAD/EMTDC version 4.6. The system stability conditions are analysed from frequency response
plots obtained through MATLAB R2012b platform.
Keywords: Battery, Chattering, Enhanced Exponential Reaching Law (EERL), Sliding Mode Controller (SMC),
Super Twisting Algorithm, buck/boost converter, Uninterruptible Power Supply (UPS).
Big Data and Development of Smart City: System Architecture and Practical Public Safety Example
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DOI: https://doi.org/10.2298/SJEE2003337S
Abstract: The concept of Smart City started its development path around
two to three decades ago; it has been mainly influenced and driven by radical changes in technological,
social and business environments. Big Data, Internet of Things and Networked Cyber-Physical Systems,
together with the concepts of Cloud, Fog and Edge Computing, have tremendous impact on the development of Smart City,
reforming its frame and tasks and redefining its requirements and challenges. We consider feasible
architectures of the IT infrastructure and signal processing, taking into account aspects of Big Data,
followed by summary of benefits and main challenges, like security of infrastructure and private data.
As a practical example we present a public safety application of multi-sensor imaging system:
a smart device with target detection subsystem based on artificial intelligence used for activation of target tracking.
The experiments have been performed in the cities of Abu Dhabi and Belgrade, which have very different environment.
The experiments have shown the effects of video-streaming compression on thermal imagers and the importance of
distributed processing power that optimizes requirements for amount of transmitted data and delay.
Keywords: Smart City; Big Data; Internet of Things; Cloud, Fog and Edge Computing;
Multi-Sensor Imaging Systems, Public Safety.
Malware Command and Control Over Social Media: Towards the Server-less Infrastructure
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(5.50 MB)
DOI: https://doi.org/10.2298/SJEE2003357R
Abstract: Intrusions into the computer systems are becoming increasingly sophisticated.
Command and Control (C2) infrastructure, which enables attackers to remotely control infected devices, is a critical component.
Malware is set to connect to C2 servers to receive commands and payloads, or upload logs or stolen files.
Since techniques for detecting traditional C2 servers are also advancing, attackers look for ways to make C2
communication stealth and resilient. Increasingly, they hide C2 communications in plain sight,
in particular on social media and other cloud-based public services. In this paper, we identify several emerging trends
in the use of social media for C2 communications by providing a review of the existing research,
discuss how attackers could combine these trends in the future to create a stealth and resilient server-less C2 model,
look at possible defence aspects, and suggest further research.
Keywords: Command and control, Botnet, Social media, Encryption, Security.
Analysis of Conductive and Convective Transfers in a Double Salience Switched Reluctance Machine by Analytical Coupling-2D Finite Elements
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(2.76 MB)
DOI: https://doi.org/10.2298/SJEE2003377S
Abstract: The work presented in this paper concerns the study of the thermal
behavior due to copper losses and iron losses of a switched reluctance machine with double salience (SRM6/4) by analytical
coupling – 2D finite elements. Calculation by analytical methods of the conduction coefficients in the radial and
axial direction as well as the convection coefficients in the air gap of this machine are presented.
The values of these found coefficients are used to solve the transient thermal problem for this device using the ADEMEF2D software.
The obtained results show a very large increase in temperature at the winding. Heat conduction in both radial and axial
directions has a very large effect on the temperature value in all regions of the SRM6/4.
Keywords: Switched reluctance machine, Thermal analysis, Finite elements.
Authentication Algorithm for Internet of Things Networks Based on MQTT Protocol
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(2.56 MB)
DOI: https://doi.org/10.2298/SJEE2003389D
Abstract: The authentication algorithm for machine-to-machine communication devices via
the MQTT Protocol is considered, which allows verifying the device legality without sending the password.
The algorithm protects the Internet of things network from unauthorized access, ensures confidentiality by generating
a common session key, and provides protection against attacks of the "man in the middle" and others.
The obtained experiment results showed noticeable performance improvement compared to the TLS Protocol.
The cryptographic strength of the proposed algorithm is based on the discrete logarithm problem.
The main advantage of the algorithm is the ability to authenticate in one request-response cycle.
Keywords: Authentication, MQTT, Zero-knowledge, Key management, Internet of things.